page_title: Cape Fold Belt
section_title: Table Mountain Group
hierarchical_section_title: Cape Fold Belt / Cape Supergroup / Table Mountain Group
caption_attribution_description: English: A view of the upper hairpin bend on Ou Kaapse Weg as it winds on to the Silvermine Plateau, on the Cape Peninsula. In the cutting, on the right hand side of the road, the transition between the lowermost layer of the Table Mountain Group, the Graafwater Formation, and the one above it, the Table Mountain Sandstone layer or Peninsula Formation, can be clearly seen.
context_page_description: The Cape Fold Belt is a fold and thrust belt of late Paleozoic age, which affected the sequence of sedimentary rock layers of the Cape Supergroup in the southwestern corner of South Africa. It was originally continuous with the Ventana Mountains near Bahía Blanca in Argentina, the Pensacola Mountains, the Ellsworth Mountains and the Hunter-Bowen orogeny in eastern Australia. The rocks involved are generally sandstones and shales, with the shales persisting in the valley floors while the erosion resistant sandstones form the parallel ranges, the Cape Fold Mountains, which reach a maximum height of 2325 m at Seweweekspoortpiek.
  The Cape Fold Mountains form a series of parallel ranges that run along the south-western and southern coastlines of South Africa for 850 km from the Cederberg 200 km to the north of the Cape Peninsula, and then along the south coast as far as Port Elizabeth, 650 km to the east.
context_section_description: With the widening and deepening of the rift valley, the entire southern portion of what was to become South Africa, as far as a line extending from Calvinia in the west to East London in the east, plus the KwaZulu-Natal coastline, became flooded, leading to a seaway across the southern and eastern parts of the country, called the Agulhas Sea. The sea floor consisted of the Klipheuwel Group in the west, the Natal Group in the east, and eroded pre-Cambrian rocks in between.
   
  The first sediments into the initially still shallow, possibly inland, sea were alternating layers of maroon-colored mudstones and buff-colored sandstones, each mostly between 10 and 30 cm thick. The mudstone units commonly display ripple marks from the ebb and flow of tidal currents, as well as polygonal sand-filled mud cracks that indicate occasional exposure to desiccation. This layer, known as the Graafwater Formation, reaches a maximum thickness of 400 m, but on the Cape Peninsula it is only 60–70 m thick. No fossils have been found in the Graafwater rocks, but shallow-water animal tracks have been found. A particularly good example of these tracks can be viewed in the foyer of Geology Department of the University of Stellenbosch, where a slab of Graafwater rock from the Cederberg mountains has been built into the wall.
  The cutting for Chapman's Peak Drive, on the Cape Peninsula, is carved into the Graafwater Formation which overlays the Cape Granite basement rock below the road. The Graafwater Formation can also be clearly seen in the cutting on the second hairpin bend as the Ou Kaapse Weg (road) goes up the slope from Westlake on to the Silvermine plateau. In the cutting one can also see the abrupt and obvious transition into the Peninsula Formation above it. Looking up the slope from below to the first hairpin bend, the granite basement on which the Graafwater formation rests is visible. And in the cutting at the first hairpin bend, the ocher-colored, gritty clay into which the granite weathers is clearly displayed.
  With further subsidence of the rift valley floor, and possibly breaking through to the ocean, the sediments abruptly become more sandy, indicative of a sudden increase in the depth of the Agulhas Sea (see photograph on the right). A deposit, known as the Peninsula Formation (also often referred to as Table Mountain Sandstone), consisting of thickly layered quartzitic sandstone, with a maximum thickness of 2000 m, was laid down. These sandstones are very hard, and erosion resistant. They therefore form the bulk of mountains and steep cliffs and rugged crags of the Cape Fold Belt, including the upper 600 m of the 1 km high Table Mountain, below which Cape Town is situated. It contains no fossils.
  The Peninsula formation can be traced from 300 km north of Cape Town (i.e. about 50 km north of Vanrhynsdorp on the West Coast), southwards to Cape Town and then eastwards to northern KwaZulu-Natal, a total distance of approximately 1800 km, roughly along the South African coastline. Only the section between Clanwilliam (approximately 200 km north of Cape Town) and Port Elizabeth (approximately 650 km east of Cape Town) is folded into the Cape Fold Mountains.
  During the laying down of the Peninsula Formation sediments, the western portion of the region was covered for a brief period of time by glaciers. The diamictite sediments that were laid down by these glaciers, or in glacial lakes, are known as the Pakhuis and Cederberg Formations. A small patch of Pakhuis tillite occurs on the top of Table Mountain at Maclear's Beacon, but most of the Pakhuis and Cederberg Formations are found as a thin layer (on average only about 60 m thick) in the Peninsula Formation rocks of the more inland mountains to the west of a line between Swellendam and Calvinia. These diamictite rocks are composed of finely ground mud, containing a jumble of faceted pebbles. They can easily be recognized at a distance as this formation readily erodes into fertile, gently sloping, green swaths in a landscape where this contrasts starkly with the bare rocky surfaces of the q
caption: A view of the cutting at the second hairpin bend on Ou Kaapse Weg, as it winds on to the Silvermine Plateau. The transition between the lowermost layer of the Table Mountain Group on the Cape Peninsula – the Graafwater Formation – and the layer above it, the Table Mountain Sandstone or Peninsula Formation, can be clearly seen. The very abrupt transition between them suggests that the Aghulas Sea was initially (during the Graafwater period) an area of inland drainage, possibly below sea level (comparable to the Dead Sea in the Middle East today). When the rift extended into the ocean, the rift valley suddenly flooded to become a deep water passage similar to the Red Sea today. The photograph was taken at an elevation of 250 m.
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